diff --git a/src/common/reservation.ts b/src/common/reservation.ts
index 1347901..b8cfd30 100644
--- a/src/common/reservation.ts
+++ b/src/common/reservation.ts
@@ -62,7 +62,7 @@ export class Reservation {
    */
   public isAvailableForReservation(): boolean {
     return (
-      Math.ceil(this.dateRange.start.diff(dayjs(), 'days', true)) <=
+      Math.floor(this.dateRange.start.diff(dayjs(), 'days', true)) <=
       RESERVATION_AVAILABLE_WITHIN_DAYS
     )
   }
diff --git a/tests/unit/common/reservation.test.ts b/tests/unit/common/reservation.test.ts
index 116f59e..61fb3e9 100644
--- a/tests/unit/common/reservation.test.ts
+++ b/tests/unit/common/reservation.test.ts
@@ -32,7 +32,7 @@ describe('Reservation', () => {
   test.each([
     { reservationDate: dayjs().add(7, 'days'), expected: true },
     { reservationDate: dayjs().add(1, 'days'), expected: true },
-    { reservationDate: dayjs().add(8, 'days'), expected: false },
+    { reservationDate: dayjs().add(8, 'days').add(5, 'minutes'), expected: false },
   ])(
     'will properly mark reservation availability according to date',
     ({ reservationDate, expected }) => {